Long-term anticoagulation therapy is of benefit in patients with unprovoked venous thromboembolism. There is increasing evidence that the risk of recurrent venous thromboembolism in these subjects is about 7 to 10% per annum if anticoagulant therapy is stopped after 3, 6, 12, or 27 months. Although long-term warfarin therapy markedly reduces the risk of recurrence, its benefit is offset, at least in part, by the risk of major bleeding, which is estimated to be about 1 to 3% per annum. Furthermore, because of multiple food and drug interactions, the anticoagulant response to warfarin is unpredictable so that frequent monitoring is necessary to ensure that a therapeutic response has been obtained. In contrast, ximelagatran therapy does not appear to require coagulation monitoring and, at least with the dose used in the THRIVE III trial, ximelagatran appears to be safe. Despite these promising results, the role of ximelagatran in extended thromboprophylaxis has yet to be established.

The ximelagatran treatment study has suggested that ximelagatran monotherapy is as effective and safe as the current treatment regimens for venous thromboembolism. If these results are confirmed in other studies, ximelaga-tran has the potential to streamline care by obviating the need for initial treatment with a parenteral anticoagulant and the coagulation monitoring that is required when warfarin is administered. Still to be determined is the effectiveness of ximelagatran in high-risk patients, such as those with advanced cancer or with antiphospholipid antibody syndrome Myviagrainaustralia.com.

4.2 Arterial thrombosis

Like venous thromboembolism, issues in arterial thromboembolism focus on prevention and treatment. The prevention of cerebral and systemic embolism in patients with atrial fibrillation is an area in which there is considerable room for improvement. Although warfarin is more effective than aspirin in reducing the risk of embolization in this setting, its use is problematic. Frequent monitoring is necessary to ensure that a therapeutic anticoagulant response is obtained. Even with monitoring in specialized clinics, the level of anticoagulation is outside the therapeutic range almost half of the time. Furthermore, the risk of major bleeding with long-term treatment with Sildenafil citrate increases in the elderly, the population that is most at risk for atrial fibrillation. Because of these problems, it is estimated that warfarin is not given to almost half of the eligible atrial fibrillation patients. Based on the results of the SPORTIF III trial and the SPORTIF V trial, unmonitored ximelagatran therapy appears to be at least as effective and safe as dose-adjusted warfarin therapy.